A tag or label on the product responds to a field at the exit, and the antenna detects that response and alarms - unless the tag has been removed or deactivated at the till.

Antennas at the exit generate a field and listen for the characteristic response of a live tag passing through it.

Hard tags are removed with a detacher at the point of sale. Adhesive labels are deactivated by a pad or by the scanner, which permanently disables the response.

The alarm is a presence detection, not an identification: with the common technologies the system knows a live tag passed, not which product it was on.

Item-level RFID is the exception. It reads a unique identity, so the system can name the item and check whether it was sold.

The fourth part is the human response, and it is the one that most often has no written procedure behind it.

Acoustomagnetic for wide aisles, metal-rich stock and high value; radio frequency for high-volume packaged goods on cheap labels; RFID where stock accuracy is wanted as well.

Acoustomagnetic systems handle wider exits, cope better with foil and metal, and their tags cost more. Supermarkets, pharmacies and stores with metal shelving near the exit favour them.

Radio frequency systems use flat adhesive labels that cost very little, which makes them the economic choice where thousands of items are tagged. Their weaknesses are metal, foil and liquid.

RFID reads item identity, which turns loss prevention into inventory management. The tags cost more and the business case usually rests on stock accuracy rather than theft.

Mixing technologies in one store is possible but needs separate antennas and doubles the till-side process.

Whatever is chosen, the supply chain matters: source-tagged goods arrive with a label matched to one technology, so the store's choice may already be constrained.

Almost always because a label was not deactivated, and after that because of interference, nearby stock or a tag brought in from another store.

Un-deactivated labels are the dominant cause, and the fix is process rather than hardware: deactivation has to be part of the scanning motion, not a separate step someone remembers.

Goods on shelves too close to the antenna can be detected as customers pass, which is a layout problem.

Electrical interference from lighting, motors, refrigeration and other radio equipment affects both main technologies and is worst near the exit.

Customers carrying tagged goods bought elsewhere set off any system using the same technology, and there is no way to prevent it.

Track the false alarm rate deliberately. Once staff stop responding, the system has stopped working, and the point at which that happens is usually visible in the data.

Follow a written procedure - and in most jurisdictions an EAS alarm alone is not grounds to detain or search anyone.

The legal powers of retail staff to stop, detain or search a customer differ substantially between countries and sometimes between regions, and getting this wrong creates liability far larger than the stock.

The safe general procedure is polite: acknowledge the alarm, ask the customer whether they would mind the goods being rechecked, and treat a refusal as the end of the matter unless local law and company policy say otherwise.

Staff need training in that procedure and the confidence that following it is supported.

Every alarm should be logged with its outcome, because the pattern is what identifies a deactivation failure at a particular till or a genuine theft problem.

Take legal advice on the local position and put it in the procedure rather than leaving staff to improvise.

Yes wherever suppliers will do it - it removes the store labour entirely and puts the label somewhere it cannot easily be found.

Applying labels in store is slow, it happens in a back room rather than at the shelf, and it is the first task to lapse on a trading day that gets away from the team.

Source-tagged goods arrive protected, which also closes the gap between delivery and the shop floor.

A label applied during packing can be placed inside the packaging or under a label, where it is far harder to locate and peel off.

The obstacle is commercial: it is a supplier programme requiring agreement on technology, placement and cost, which is why it is usually driven by large retailers or buying groups.

Where suppliers will not participate, in-store tagging with a defined placement standard is the fallback - and the standard matters, because a label always in the same place is a label always found.

It deters and detects opportunistic theft of tagged items. It does very little about organised theft, till fraud, or losses that never involve the shop floor.

The deterrent effect is real and is most of the value: visible antennas and tags change behaviour before anything is taken.

Organised offenders carry foil-lined bags, detach tags in fitting rooms and know which items are not tagged. EAS slows them rather than stopping them.

A significant share of retail loss has nothing to do with the exit: process failures, damage, mis-scanning, delivery discrepancies and internal theft.

That is why EAS sits alongside merchandise protection on the display, video at the till, and stock accuracy work.

Measure what is actually being lost before deciding how much to spend at the exit. The answer frequently redirects the budget.

Antennas at each exit, deactivation or detaching at every till, a tagging process, and a power and data path to each pedestal.

Antenna spacing is set by the technology and the aisle width, and wide entrances need either more pedestals or a technology that tolerates the distance.

Siting has to avoid metal shelving, refrigeration, motors and other radio equipment, and that survey is worth doing before committing to a layout.

Every till needs deactivation or a detacher, and the counter layout has to make it part of the natural scanning movement.

Power at the entrance is often the practical constraint in an existing store, along with floor boxes and cable routes across the entrance.

Allow for tuning after opening. Systems are commissioned to a sensitivity that then needs adjusting against real traffic and real false alarms.

Yes - footfall counting, deactivation verification and metal-detection for foil-lined bags are common additions.

People counting in the pedestals gives conversion rate and staffing data from hardware already at the door, and is frequently the easiest data a store can acquire.

Deactivation verification checks that a label passing the antenna was properly killed, which distinguishes a process failure from a theft.

Metal detection identifies foil-lined bags used to defeat the system, which is the signature of organised rather than opportunistic theft.

Alarm logging with time stamps allows the false alarm pattern to be analysed by till, by hour and by day.

These are usually licensed options rather than included features, so check what the quoted pedestal actually does before assuming.

With merchandise protection devices - safer cases, cable locks, locking hooks and anti-sweep fittings - because EAS at the exit does not stop the item leaving the shelf.

Open display sells considerably more than locked cabinets, so the aim is to keep goods handleable while making removal slow, awkward or noisy.

Safer cases enclose small high-value items in a transparent box opened at the till.

Cable and alarm locks tether powered display items so they can still be demonstrated and used.

Locking hooks and stop locks prevent a whole peg being swept in one movement.

These devices work with EAS rather than instead of it, and the till-side process for removing them has to be as well drilled as the deactivation process.

By alarm rate and outcome per exit and per till, by shrinkage on protected versus unprotected lines, and by how consistently items are actually tagged.

An alarm log with outcomes distinguishes false alarms from genuine detections and shows which till is failing to deactivate.

Comparing shrinkage on protected and unprotected product lines is the closest thing to a controlled measurement most retailers can get.

Tagging compliance is worth auditing directly. Systems commonly degrade because tagging quietly stops, not because the hardware fails.

Staff response rate matters as much as detection: an alarm with no response is a detection that achieved nothing.

Review quarterly with store management rather than treating the installation as finished at handover. Almost all of the value is in the operating discipline.